The present invention relates to bend-shaping method and apparatus for a glass plate for transporting machines such as automobiles, ships, railways, airplanes and so on or for various usages for buildings and so on. In particular, the present invention relates to a bend-shaping method and apparatus for a glass plate suitable for bend-shaping a glass plate for windows of automobiles.
There has been known a method for bend-shaping a glass plate by heating the glass plate to around a softening temperature in a heating furnace and transferring the glass plate on a roller conveyor comprising a plurality of curved rollers (in, for example, U.S. Pat. No. 4,123,246). According to this method, the softened glass plate falls by its own weight and the glass plate is bent to meet a curvature of the rollers.
Further, there has been known a method for bend-shaping a glass plate by heating the glass plate to around a softening temperature in a heating furnace and transferring the glass plate by means of a plurality of rollers inclined in a transferring direction so that the transferring path is curved (in, for example, U.S. Pat. No. 4,820,327). According to this method, the softened glass plate falls by its own weight and the glass plate is bent to meet a curvature of the transferring path.
In description, xe2x80x9cbend-shaping in a direction perpendicular to a transferring directionxe2x80x9d means that the shape of a bend-shaped glass plate is a shape curved around an axis of transferring direction. In other words, the bend-shaped glass plate has a curved shape in cross-section taken vertically along the axis of transferring direction. xe2x80x9cBend-shaping in (along) a transferring directionxe2x80x9d means that the shape of a bend-shaped glass plate is a shape curved around the axis perpendicular to the transferring direction. In other words, the bend-shaped glass plate has a curved shape in the cross-section taken vertically along the axis perpendicular to the transferring direction. With respect to the shape of a curved plane formed by a plurality of rollers as described after, phrases xe2x80x9cbent in (along) a transferring directionxe2x80x9d, xe2x80x9ccurved in a transferring directionxe2x80x9d or the like have the same meaning as xe2x80x9cbend-shaped in (along) a transferring directionxe2x80x9d. A phrase xe2x80x9cbend-shaped in a direction perpendicular to a transferring directionxe2x80x9d is also applicable to description about a curved plane with respect to a direction perpendicular to a transferring direction.
In this description, xe2x80x9cperpendicular to a certain directionxe2x80x9d means a direction perpendicular to certain direction on a horizontal plane. Further, xe2x80x9cupperxe2x80x9d or xe2x80x9clowerxe2x80x9d means xe2x80x9cupperxe2x80x9d or xe2x80x9clowerxe2x80x9d with respect to a horizontal plane in this description.
In recent years, there is an increasing demand of production of small quantity and large variety in automobile industries, and glass plates having various curvatures are needed in response to models of automobiles. In a method described in U.S. Pat. No. 4,123,246, it was necessary to exchange rollers to those having a curvature corresponding to a model of automobile to be manufactured. The exchanging work took much time, and it was necessary to prepare rollers having a curvature required for a model to be manufactured. In this method, glass plates are transferred in a direction perpendicular to a direction to be bent. In bend-shaping a glass plate for a side window of an automobile, the direction of a 15 side of the glass plate when it is fitted to an automobile, corresponds to the direction of extending of the rollers. In such state of fitting, a distortion appearing in the glass plate due to the contact of a roller having a distortion is conspicuous.
According to the method described in U.S. Pat. No. 4,820,327 (""327 method), it was necessary to change the arrangement of rollers so as to form a transferring path having a curvature which corresponds to a model to be manufactured.
Such change took much time.
Further, in the ""327 method, the transferring direction of the glass plate is changed to a vertical direction. Therefore, the entire equipment to be used for the ""327 method is inevitably large. Further, since the glass plate is transferred against the gravity, it is difficult to transfer the glass plate at a high speed, and a special mechanism for preventing the slippage of the glass plate has to be provided. Further, the transferring direction has to be changed from the vertical direction to a horizontal direction for the glass plate having been subjected to bend-shaping and tempering by cooling. A mechanism for changing the transferring direction is complicated, and there is a risk of a damage in the glass plate.
It is an object of the present invention to eliminate the disadvantages of the conventional techniques and to provide new bend-shaping method and apparatus for a glass plate which have been known conventionally.
The present invention has been made in consideration of the above-mentioned problems and to provide a bend-shaping method for a glass plate comprising heating a glass plate to a bend-shaping temperature in a heating furnace and transferring the heated glass plate along a transferring plane formed by a plurality of rollers of a roller conveyor during which the glass plate is bend-shaped to have a predetermined curvature due to the dead weight of the glass plate, the bend-shaping method for a glass plate being characterized in that said rollers for forming a transferring plane are moved vertically depending on a position of transfer of the glass plate to form a curve in at least a part of the transferring plane so that a predetermined curved plane is formed at the position of transfer where the glass plate is, and the curved plane is shifted, as the propagation of a wave, from an upstream side to a downstream side of the roller conveyor whereby the glass plate is bend-shaped to have a predetermined curvature along the curved plane.
Further, the present invention provides a bend-shaping method for a glass plate comprising heating a glass plate to a bend-shaping temperature in a heating furnace and transferring the heated glass plate along a transferring plane formed by a plurality of rollers which are arranged side by side in a transferring direction of the glass plate during which the glass plate is bend-shaped to have a predetermined curvature due to the dead weight of the glass plate, the bend-shaping method for a glass plate being characterized in that a plurality of rollers at a position where the glass plate is transferred are moved vertically with the transfer of the glass plate so that a predetermined curved plane, which is curved in the transferring direction of the glass plate, is formed in at lease a part of the transferring plane by means of the plurality of rollers at said position, and each of said rollers is sequentially moved vertically with the transfer of the glass plate to shift the curved plane in the transferring direction of the lass plate with the transfer of the glass plate whereby the glass plate is bend-shaped so as to meet the curved lane during the transfer of the glass plate.
Further, the present invention provides a bend-shaping apparatus for a glass plate comprising a heating furnace for heating a glass plate to a bend-shaping temperature and a shaping means, located at a downstream side of the heating furnace, for bend-shaping the glass plate to have a predetermined curvature, the bend-shaping apparatus for a glass plate being characterized in that said shaping means comprises a roller conveyor comprising a plurality of rollers which form a transferring plane for transferring the glass plate, a vertical direction driving means for moving vertically the plurality of rollers, and a control means which controls the driving means to move vertically the rollers so that at least a part of the transferring plane is bent to have a curvature which corresponds to a curvature of the glass plate to be formed whereby a predetermined curved plane is formed by the rollers at the position where the transferred glass plate is, and the curved plane is shifted, as the propagation of a wave, from an upstream side to a downstream side of the roller conveyor, wherein the glass plate is transferred during the shift of the curved plane whereby the glass plate is bend-shaped to have a predetermined curvature to meet the curved plane.
Further, the present invention provides a bend-shaping apparatus for a glass plate comprising a heating furnace for heating a glass plate to a bend-shaping temperature and a shaping means, located at a downstream side of the heating furnace, for bend-shaping the glass plate to have a predetermined curvature, the bend-shaping apparatus for a glass plate being characterized in that said shaping means comprises a roller conveyor comprising a plurality of rollers which are arranged side by side in the transferring direction of the glass plate to form a transferring plane for transferring the glass plate, a vertical direction driving means for moving vertically the plurality of rollers, and a control means which controls the driving means to form a predetermined curved plane curved in the transferring direction of the glass plate in at least a part of the transferring plane by the rollers at the position where the transferred glass plate is, and to move sequentially in a vertical direction the plurality of rollers with the transfer of the glass plate whereby the curved plane is shifted in the transferring direction of the glass plate.
Specifically, each of the rollers is moved vertically with the transfer of the glass plate. With such vertical movement, a curved plane is formed by a plurality of rollers at a position where the transferred glass plate is, and the curved plane is shifted to the transferring direction of the glass plate. In other words, the curved plane corresponds to a wave plane of downward convex shape or a wave plane of upward convex shape; each of rollers corresponds to an oscillating element of the wave, and a stroke length in the vertical movement of each roller corresponds to an amplitude of the wave respectively. The propagation of a wave is generated by providing a phase difference to the vertical movement of each of the rollers so that the phase of each roller as each oscillating element is sequentially changed toward a downstream in the transferring direction, whereby the curved plane is shifted to the transferring direction of the glass plate.
For the vertical movement of each of the rollers, it is preferable that a one cycle of movement is formed by a series of movement from an original position in a vertical direction via descendingxe2x86x92ascending to return the original position. In this case, each of the rollers takes (a: an initial state) which represents the beginning of descending at the time when a front edge in a transferring direction of a glass plate as one unit is transferred to it, (b) which represents a one cycle on a movement of descendingxe2x86x92ascending during the transfer of the glass plate as one unit, and (c: an end state) which represents the movement of returning to the original position at the time when a rear edge in the transferring direction of the glass plate as one unit is transferred to it. Thus, a roller performs a one cycle of vertical movement from the initial state to the end state while the glass plate as one unit has passed on the roller. When a plurality of glass plates are successively bend-shaped, glass plates as each unit are successively transferred. Accordingly, each of the rollers is repeatedly moved vertically in the order of (a), (b) and (c) for subsequent glass plates as each unit. When a movement of ascendingxe2x86x92descending is caused on each of the rollers, the initial state is determined so that the beginning of ascending is at the time when a front edge in the transferring direction of the glass plate as one unit is transferred to it.
When a curved plane having a downward convex shape is to be formed by causing the vertical movement on each roller, the glass plate as one unit is transferred as follows. When a front edge and a rear edge in the transferring direction of the glass plate are located on certain rollers, those rollers are in an initial state (an end state). Accordingly, the positions in a vertical direction of the front edge and the rear edge in the transferring direction of the glass plate are maintained at positions corresponding to the initial state on each roller. A height level in a vertical direction of an imaginary plane (which is horizontal) formed by each of the rollers in the initial state is referred to as xe2x80x9ca transferring levelxe2x80x9d. On the other hand, each of the rollers, which corresponds to an intermediate portion of the glass plate, as a portion between the front edge and the rear edge in the transferring direction of the glass plate, is in an intermediate state in one cycle of vertical movement. Accordingly, the intermediate portion of the glass plate is lower in position than the transferring level (the intermediate portion falls downward). Accordingly, the glass plate as one unit is transferred in a manner that the intermediate portion is lower in position than the transferring level while the front edge and the rear edge in the transferring direction are maintained at the transferring level. In a case of forming a curved plane having an upward convex shape, the intermediate portion is upper in position than the transferring level.
xe2x80x9cA glass plate as one unitxe2x80x9d means usually a single glass plate. In a case of transferring two or more glass plates in a stacked state according to requirement, the two or more glass plates can simultaneously be bend-shaped. Thus, xe2x80x9ca glass plate as one unitxe2x80x9d includes two or more glass plates in a stacked state. According to the bend-shaping method and apparatus of the present invention, a glass plate as one unit can successively be bend-shaped and a plurality of glass plates as one unit can successively be bend-shaped. Whether a glass plate as one unit is a single glass plate or a glass plate is a plurality of glass plates in a stacked state does not influence largely the basic operation of the bend-shaping method and apparatus for a glass plate of the present invention. From this reason, the words xe2x80x9cone unitxe2x80x9d can be omitted in this description.
Since the rollers are moved vertically, a transferring rate of a horizontal component of the glass plate depends on a position in a vertical direction of each roller. In this case, if angular speeds of rollers are constant, the transferring rate of a horizontal component of a roller at a lower side is higher than that of a roller at an upper side. If such imbalance of speed is generated, a slip takes place between a roller and the glass plate whereby the glass plate is apt to be damaged. Accordingly, it is preferable to provide a rotation driving means for rotating independently a plurality of rollers and a control device for controlling the rotation driving means so that transferring rates of a horizontal component of the glass plate become equal. With such measures, the above-mentioned disadvantage can be eliminated, and a glass plate without flaws can be obtained.
The curved plane formed by rollers has the meaning as follows. First, a central axial line is assumed for each roller. Since each of the central axial lines extends in a direction perpendicular to the transferring direction, an imaginary curved plane is formed by connecting smoothly each of the central axial lines. The imaginary curved plane corresponds to a curved plane formed by each of the rollers. Since each of the rollers is in fact has a finite thickness, the curved plane formed by each of the rollers is slightly different from the imaginary curved plane. Namely, the radius of curvature of the curved plane formed by each of the rollers is slightly smaller (about a radius of a roller) than the radius of curvature of the imaginary curved plane. Accordingly, the curved plane formed by each of the rollers corresponds to a curved plane which is slightly smaller than the radius of curvature of the imaginary curved plane.
A predetermined curved plane formed by each of the rollers is a curved plane required depending on positions of rollers for transferring the glass plate. Specifically, at the extremely downstream position in a zone for bend-shaping the glass plate, a curved plane to be formed by the rollers at this position provides a curved shape which is generally in agreement with a curved shape of the glass plate finally obtainable, in the transferring direction of the glass plate.
As an example, a curved plane formed by rollers which are located at an upstream side with respect to the extremely downstream position has a radius of curvature which is larger than a curved plane formed by the rollers at the extremely downstream position. Going to further upstream side, a curved plane formed by rollers at an upstream side has a further larger radius of curvature.
As another example, it is possible that at every position of a zone for bend-shaping the glass plate, the curved plane to be formed by rollers is rendered to be a curved shape which is generally in agreement with a curved shape in the transferring direction of the glass plate finally obtainable. In any case, in order to bend-shape the glass plate into a curved shape of the glass plate finally obtainable, the curved plane to be formed by rollers is rendered to a curved plane determined in correspondence with a position where the transferred glass plate is. In this case, the shape of the curved glass plate is determined in consideration of the thickness of the glass plate and the temperature of the glass plate. It is preferable to constitute an apparatus in a manner capable of determining appropriately as to how the shape of the curved plane is changed (or a predetermined curved shape is provided) depending on these conditions.
The glass plate may not be bent instantaneously due to the own weight. Accordingly, it is preferable that the radius of curvature of a curved plane formed by each of the rollers is reduced gradually from an upstream side to thereby form a gradually reduced radius of curvature whereby a predetermined curved shape of the glass plate can be finally obtained at the extremely downstream position, from the viewpoint of transmitting a sufficient driving force by each of the rollers to the glass plate.
The above-mentioned bend-shaping method and apparatus for a glass plate are to bend-shape a glass plate only in a single direction of transferring direction of the glass plate. In a case of bend-shaping a glass plate to have a desired shape, e.g., a shape obtained by bend-shaping the glass plate only in a single direction (a simply curved shape), a shape having portions each having a different curvature in the glass plate of simply curved shape (a combined curved shape), a shape obtained by bending a glass plate in a plurality of directions (a complexly curved shape) and so on, it is preferable to add one or more than two measures, as described below, to the above-mentioned bend-shaping method and apparatus for a glass plate.
(1: Correction of a curved shape in a glass plate)
A pressing roller is additionally provided above the rollers. The pressing roller is located in a normal direction on a curved plane and a glass plate is held between the pressing roller and rollers to bend-shape the glass plate so as to meet the curved plane. At this moment, the pressing roller is always located in a normal direction onto the curved plane by means of a pressing roller moving means.
(2: A combined curved shape)
A pressing roller is separately provided above and between adjacent two rollers. A portion of a glass plate, corresponding to a position between the two rollers is pressed by the pressing roller to apply a load to that portion of the glass plate whereby the glass plate is bend-shaped. In this case, a load is applied to the glass plate by moving forward and backward the pressing roller to the transferring plane by means of the pressing roller moving means.
(3: A combined curved shape)
The curved plane is formed so as to have a plurality of radius of curvatures in the transferring direction.
(4: A complexly curved shape)
Air is injected to at least one of an upper face and a lower face of a bend-shaped glass plate from a plurality of air injecting means arranged above and below the transferring plane, the air injecting means being located at a downstream side of the rollers for bend-shaping the glass plate, to bend-shape the glass plate in a direction perpendicular to the transferring direction while a balance of cooling to the upper plane and the lower plane of the glass plate is adjusted.
(5: A complexly curved shape)
Rollers 20 are arranged horizontally in a side-by-side relation in the transferring direction and the rollers are rendered to be inclined with respect to a horizontal plane. Further, the rollers are arranged so that the direction of inclination of rollers adjacent to each other is alternately different (right side lifting and left side lifting in a front view viewed from a downstream side in the transferring direction). A curved plane bent in a direction perpendicular to the transferring direction is formed by adjacent two rollers to thereby bend-shape the glass plate in a direction perpendicular to the transferring direction.